Identification unit

ABSTRACT

An identification unit including a memory unit operable to store an identification that distinguishes the identification unit from other identically constructed identification units, an ultrasonic receiver, a radiation transmitter, a radiation receiver and a control unit operable to carry out an ultrasound propagation time measurement depending on a synchronization signal received by the radiation receiver and operable to transmit a result with the aid of the radiation transmitter. At least one of a luminous unit and an optical signaling unit is driven via the radiation unit.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No. 10/579,347filed on Apr. 13, 2007, which application is a national stageapplication under 35 U.S.C. §371 of PCT Application No.PCT/EP2004/052739 filed Oct. 29, 2004 which claims priority under 35U.S.C. §119 from German Patent Application No. 103 52 774.5 filed Nov.12, 2003, the disclosures of each of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION Field of the Invention

The disclosure relates to a locating arrangement, particularly abore-box localization system, an identifying unit and a method fordetermining location

More particularly, the invention relates to a locating arrangement whichcan be used to determine the position of at least one identificationunit. The identification unit may be connected to a manufacturing batchcontaining a plurality of workpieces that are to be processed in thesame way, e.g. semiconductor wafers. A batch may contain, for example,approximately 50 or 25 semiconductor wafers, i.e. two racks or one rack.

SUMMARY OF THE INVENTION

It is an object of the invention to specify a simple locatingarrangement that enables a high locating accuracy. In particular, systemresources that can also be utilized for communication are intended to betaken up to the least possible extent. Moreover, the intention is tospecify an identification unit to be located and a locating method.

The object in respect of the locating arrangement is achieved by meansof an arrangement having the features disclosed herein. Developments arealso disclosed herein.

Locating in the near range with electromagnetic waves, such as radiowaves or light or infrared light, is technically possible butcomplicated in terms of circuitry because excessively stringentrequirements are made of the processing times of the circuit on accountof the short signal propagation times. Ultrasound having a propagationspeed in air at room temperature of approximately 340 m/s is moresuitable. Propagation times of the signals in the near range are thuse.g. less than 50 milliseconds. Such propagation times can be detectedwith a tenable circuitry outlay.

A locating arrangement according to the invention therefore may containa plurality of ultrasonic transmitters strung along a path, e.g. atleast three, six or nine ultrasonic transmitters. The distance betweenadjacent ultrasonic transmitters in the series is more than one meter.By virtue of this measure, transmitters can still be installed with atenable outlay even along a path of up to several hundred meters. Theactual measurement only ever requires the two nearest or only very fewtransmitters in the vicinity of the object to be located.

The determining method for determining the position is particularlysimple if, in one development, the transmitters are strung along astraight section at mutually uniform distances between mutually adjacenttransmitters. The calculation method is then in particular independentof the location, i.e. always the same for different locations.

In one development, the distance has a value in the range of from threemeters to one meter, in particular a value of 1.6 meters. The valuesmentioned are a particularly good compromise between a small number ofultrasonic transmitters, high spatial resolution and short propagationtime determination.

In a next development, the transmitters are arranged along an aisle, inparticular along an aisle in a factory building. Semiconductor wafers orother substrates for integrated electronic circuits are preferablyprocessed in the factory building.

In another development, the locating arrangement contains a drive unit,which drives the transmitters in accordance with a pulsed operating modein which ultrasonic pulses are transmitted between transmission pauses.Ultrasonic pulses are particularly well suited to the locating process.

In a next development, the drive unit works cyclically, drive signalswhich instigate the transmission of ultrasonic pulses being generatedfor the transmitters. A cycle contains at least two sections in each ofwhich a different portion of the transmitters is driven. By virtue ofthis measure, the propagation times from different transmitters can bedetermined successively without mutual interference. The number ofsections per cycle depends on a plurality of parameters, for example,the required repetition rate, the locating accuracy, the time requiredfor communication, and on hardware conditions, for example, 12ultrasonic transmitters are connected to one drive unit, so thatmultiples of 12 are preferably chosen. A suitable number of cycles maybe, for example, 36 cycles or 48 cycles.

In a next development, the drive unit may contain a plurality of groupdrive units which in each case generate the drive signals for aplurality of transmitters depending on an input signal. The drivecomplexity can thereby be reduced.

In one development, at least three further US transmitters are strungalong a further straight section at mutually identical distances betweenmutually adjacent transmitters. If the two paths lie parallel to oneanother, then locations in parallel aisles can be detected in a simplemanner. However, a two-dimensional location detection is also possible,one coordinate lying along a path and the other coordinate depending onthe path from which locating is effected.

In one development, at least two transmitters on different pathstransmit simultaneously, so that instances of influencing are precludedor greatly reduced. This can be achieved in particular if more than onetransmitter or more than three transmitters or more than sixtransmitters, relative to one of the two paths, lie between the twosimultaneously transmitting transmitters after a parallel displacementof one path to the other path.

In a next development, a region into which no ultrasonic signal of thetransmitters or only a greatly attenuated ultrasonic signal penetrateslies between the two paths. The region may be, for example, a furtheraisle between two aisles in which locating is effected. Thus, insemiconductor fabrication facilities, maintenance aisles are arrangedbetween clean room aisles. No wafers are located in the maintenanceaisles.

In one development, there are at least three further US transmittersstrung along a straight main section at mutually identical distancesbetween mutually adjacent transmitters, the main section lyingtransversely with respect to at least two secondary sections, inparticular at an angle of 90 degrees. As a result, locating can also beperformed in a main aisle that connects the transverse aisles.

In one development, the locating arrangement contains at least threeradiation receivers, in particular receivers for electromagneticradiation, such as RF (radio frequency) or radio receivers or infraredreceivers, strung along a straight section at mutually identicallydistances between mutually adjacent radiation receivers. The distancebetween adjacent receivers is at least twice as large as the distancebetween adjacent transmitters. In one refinement, the receivers servefor communication with the objects to be located. The communication mustbe effected as rapidly as possible, with the result that ultrasoundwould be too slow. In one refinement, the receivers are additionallyutilized for a coarse localization, reception levels being evaluated inplace of propagation times. As a result, the circuitry outlay is alsolow in the case of the coarse localization.

In one refinement, the distance between the receivers lies in the rangeof from three meters and up to seven meters. As a result, it is alwayspossible to determine a receiver whose reception signal, with respect toa unit to be localized, is considerably greater than that of the otherreceivers, so that the coarse localization can be carried out simply andreliably.

If, in one refinement, the receivers are arranged on the same sectionsas the transmitters, then the assembly outlay is low. If one receiver isin each case arranged between two transmitters, preferably at the samedistance from the two transmitters, then shadowing is low.

In one development, there are a plurality of connection units at each ofwhich a plurality of antenna modules are operated, an antenna modulepreferably containing a reception antenna and a plurality oftransmitters, for example, three transmitters.

In one refinement, the connection units are connected via a local datatransmission network, for example, via an Ethernet. The modularconstruction enables easy adaptation to different spatial conditions.

In a next development, the ultrasonic transmitters and the RF antennasare fixed to a ceiling or to ceiling transverse bracing.

In one development, the locating arrangement contains at least 1000 orat least 1500 identification units which have mutually differentidentifications and which are arranged in the acoustic irradiation rangeof the transmitters. By way of example, in a factory building there arethe above-mentioned number of receptacle containers to be located for aplurality of substrates for integrated circuits.

The invention additionally relates to an identification unit containinga memory unit, in which is stored an identification which distinguishesthe identification unit from other identically constructedidentification units. The identification unit additionally contains anultrasonic receiver, a radiation transmitter, a radiation receiver and acontrol unit. The control unit carries out an ultrasound propagationtime measurement depending on a synchronization signal received by theradiation receiver and transmits the result toward the outside with theaid of the radiation transmitter.

In one refinement, the identification unit contains a power-savingbistable character display unit, which displays the content to berepresented even after the operating voltage has been switched off. Asan alternative or in addition, the identification unit contains at leastone luminous unit that can be driven via the radiation receiver, forexample, a light-emitting diode. The luminous unit may identify, forexample, manufacturing units that are to be processed preferentially orparticularly quickly. An identification unit currently sought can alsobe distinguished from other identification units by means of theluminous unit, in particular by means of a flashing luminous unit, evenfrom several meters, thereby considerably facilitating the search evenif the location is approximately known. By way of example, theidentification unit sought can easily be picked out from threeidentification units within a radius of half a meter. The search enquirymay be input, for example, via a drive unit.

The disclosure additionally relates to a location determining method,having the following steps:

constructing a locating arrangement comprising a plurality of ultrasonictransmitters along at least one path,

constructing at least two radiation receivers or radiation transmittersthat in each case receive radiation from at least one region irradiatedwith sound by a transmitter,

introducing at least one identification unit into a region irradiatedwith sound by at least two transmitters,

carrying out an ultrasonic propagation time measurement from at leasttwo transmitters to the identification unit and determining at least onepropagation time datum,

determining a fine position of the identification unit depending on thepropagation time datum,

determining a coarse position of the identification unit with the aid ofat least two radiation transmitters or radiation receivers,

combining the fine position and the coarse position to form a locationdatum.

A powerful locating method is produced which is suitable in particularfor use in semiconductor fabrication facilities.

In one development of the method, the following steps are carried out:

determining the fine position by trigonometrical calculations in a planewhich contains a section in which the ultrasonic transmitters are strungand which contains the identification unit,

determining a fine position by means of only one spatial coordinate.

In comparison with a three-dimensional or two-dimensional locatingprocess that is not always necessary, the one-dimensional locatingprocess thus carried out can be carried out very accurately and with alow outlay.

The invention additionally relates to a batch box localization system,having a locating arrangement, which extensively detects the transportpaths for a plurality of batch boxes between a plurality ofmanufacturing installations and locates the batch boxes with an accuracyof less than two meters or less than one meter. In particular, thelocating arrangement according to the invention or one of itsdevelopments is used in the batch box localization system.

In one development, the batch box localization system contains acommunication system that outputs manufacturing data and/or transportdata to output units fixed to the batch boxes.

As a result, it is possible not just to collect location information andoutput information during the storage time of the batch boxes, forexample, on a shelf, but to dynamically support the entire transportprocess. The crucial principle for this is the linear concept of theantenna and transmitter installation, in particular in the center alongthe longitudinal axis of an aisle or a so-called finger. By virtue ofthis principle, the antenna density can be reduced to an extent suchthat the required performance of an extensive localization and of alocation-independent communication is achieved. The low antenna densitymakes it possible to achieve, in a synchronous communication protocolwhich is used between the RF antennas (radio frequency), the ultrasonictransmitters and the identification units and in which one cycle issubdivided into fixed time segments, a time saving of more than 70percent for the fine localization by means of ultrasound, so that 70percent of the time remains for communication processes via radio.

It becomes possible to localize a batch box along the fingerlongitudinal axis to an accuracy of a few centimeters. By contrast, itis not possible to effect a position determination with regard to theposition in terms of the height and the width of an aisle or finger,i.e. a three-dimensional location indication. However, athree-dimensional location indication is not actually necessary for thedirecting function during transport since the accurate localization of abatch box is possible, for example, through the possibility of anoptical signaling in the form of a flip dot or a flashing orcontinuously illuminated LED or lamp at the identification unit.

Consequently, the antenna modules that can be mounted along ageometrical line crucially increase the performance of the overallsystem, can be mounted in a simple manner and are largely independent ofshelf rearrangements or relatively small conversions of the productionbuilding.

The invention thus solves the technical problem of planning, control,optimization and monitoring of the transport process in flexibleproduction, in particular wafer production. The wafer boxes aretransported automatically, for example, by means of a conveyor belt, ormanually, for example by means of transport carts. In the case of aproduction program oriented in customized fashion, the use of fullyautomatic, rigid transport systems often cannot be implemented with atenable outlay on account of the lack of flexibility of the transportprocesses and the high capital expenditure. This limitation is nowovercome because both extensive localization and suitable outputting oftransport directing and manufacturing information, per batch box, arecarried out at any desired point in time in the transport process, withthe result that controlling interventions by operators are possible atany time. This possibility is also referred to as a paperlessfabrication facility. It is thus possible, for example, to transport anurgent batch through manufacturing in an uncomplicated manner.

The invention specifies, in particular, an integrated transportdirecting and manufacturing information system which integrates both thepath stipulation for manual transport on the basis of a finelocalization of the batch boxes by radio and ultrasonic technology inthe entire production building and the information and routingoutputting for efficient delivery or for efficient transport of thebatch box to the next manufacturing operation. Communication to theoperators may be carried out, for example, via a radio transponder witha bistable display that is fixed to the batch box.

As explained in even greater detail further below, the system maycomprise, for example, the following components:

identification unit or DisTag (distance transponder, distance tag) as anactive radio transponder with an integrated ultrasonic receiver for finelocalization and a bistable display for displaying data,

antenna modules that are extensive and modular and contain RF antennasand ultrasonic transmitters and also integrated control devices,

data processing system or box tracking server for controlling theextensive localization and dynamic communication—-comprehending thetransport path—with the DisTag for information outputting of thetransport directing and manufacturing information.

Because of the extensive accurate detection of the spatial positions ofthe wafer boxes and also the communication possible at any point in timeby means of the handover principle within the manufacturing building,the solution affords in particular the following advantages:

extensive accurate localization with an accuracy down to a fewcentimeters,

outputting of the manufacturing and transport directing information atany time in decentralized fashion at the location of occurrence, forexample at the batch box (paperless fab), outputting of an item ofdynamic status information, for example, a reservation, batch message orurgent batch, which assists handling processes since the information isdisplayed directly at the batch box itself (paperless fab),

the manufacturing turnaround time can be shortened through minimizationof search, transport and storage operations of the batch boxes and theoptimization of the capacitor utilization of the manufacturing machinesthat is placed thereon,

an extensive localization function in conjunction with a greatly reducedinstallation outlay becomes possible on account of the high range of RFand ultrasonic technology.

BRIEF DESCRIPTION OF THE DRAWINGS

Other benefits and features of the present invention will becomeapparent form the following detailed description considered inconnection with the accompanying drawings. It is to be understood,however, that the drawings are designed as an illustration only and notas a definition of the limits of the invention.

In the drawings, wherein similar reference characters denote similarelements throughout the several views:

FIG. 1 shows the division of a building area according to the linearconcept taking account of a cluster condition,

FIG. 2 shows a section of a locating arrangement that forms a device,

FIG. 3 shows constituent parts of a drive and evaluation unit,

FIG. 4 shows an identification unit whose location is to be determined,

FIG. 5 shows the trigonometrical basic principle for determining thelinear position, and

FIG. 6 shows method steps for calculating the position of theidentification unit.

DETAILED DESCRIPTION OF THE DRAWINGS

Although the invention is explained below on the basis of a batchtracking system in semiconductor manufacturing, the disclosed inventionmay also be used in other areas, for example, in mechanical engineeringor in libraries. Although reference is made below to straight aisles,the invention may also be used in the case of path sections that arelinear piece by piece.

The combination of radio and ultrasonic technology resolves the conflictbetween efficient communication and accurate localization, i.e. theperformance both of the communication and of the localization is veryhigh. When using ultrasound (US), the challenge is as far as possiblenot to permit the time-critical processing of the ultrasonic signals tobe of significance. The speed of sound is approximately 340 m/s incontrast to the speed of light, at which radio beams propagate. Fordetermining an item of analog location information by means ofultrasound, it must be ensured that a US receiver in an identificationunit or a DisTag does not simultaneously receive two US signals whoseorigin cannot be differentiated. It follows from this that, inaccordance with an anticollision condition, US transmitters are notpermitted to transmit simultaneously which:

lie within a specific proximity region whose extent is cruciallydetermined by the range of the ultrasonic transmitter and by thereception sensitivity of the US receivers over the angle, and

which transmit within a specific time determined by a predeterminedmaximum time until the arrival of a US signal.

It is thus necessary to avoid the situation in which two US signals arereceived within this time limit and an assignment of the signal to aspecific US transmitter is not possible. In the case of a performancerequirement of e.g. “every 30 seconds updating of the spatial positionsof all batch boxes”, a plurality of ultrasonic transmitters have to bedriven simultaneously without the signals colliding with one another.This is achieved by all of the US transmitters that are drivensimultaneously being assigned to a common cluster. The method is basedon giving a minimum geometrical distance between the simultaneouslytransmitting US transmitters of a cluster. This condition is alsoreferred to as cluster condition below. The optimum design of thecluster condition, i.e. the selected distance between two UStransmitters of a cluster, is determined by the anticollision conditionand the quality of the coarse localization by radio, because the DisTagor US receiver can assign a received propagation time only in blanketfashion to all the antennas of a cluster. The assignment to a regionduring the coarse locating may be effected, for example, by means of theknowledge of the position of the radio antenna with the strongestreception level of a signal coming from the DisTag to be located.

Moreover, it must be taken into consideration that the number of UStransmitters transmitting successively in 30 seconds must be small sinceotherwise too little “radio time” is available in the e.g. synchronouscommunication protocol for:

the feedback of the propagation times and the identification numbers bythe DisTags,

the communication between a connection unit (explained in greater detailbelow) and the DisTags.

The time for transmitting the US signals including subsequentpropagation time measurement amounts to only a quarter of a cycle.

The consequence of these restrictions is that not all of the UStransmitters can be differentiated by way of the temporal position oftheir emission of ultrasound in the communication protocol. Thus, anabsolute localization solely on the basis of US propagation times is notpossible. Therefore, a coarse localization may be carried out by radiofield strength measurement, for example, an absolute coordinate, and thefine localization may be carried out via the propagation timemeasurement by ultrasound, for example, by determining a relativecoordinate.

FIG. 1 shows the division of a building area of a factory building 100according to the linear concept taking account of a cluster condition.The factory building 100 is classified, according to the linear concept,into a main aisle 102 and into transverse aisles 104, 108 and also intofurther transverse aisles 110 indicated by dots. On account of themaximum available time for a localization, which is 30 seconds in theexemplary embodiment, and the condition that all ultrasonic transmittershave to be switched three times in a cycle for redundancy reasons, theresult is a maximum cluster number of 36.

In each case three ultrasonic transmitters a, band c are combined perradio antenna 120 to 162, adjacent ultrasonic transmitters 1 a to 7 b ineach case being at a distance of 1.6 meters, as will be explained ingreater detail below with reference to FIG. 2. With these preconditions,a maximum of 12 radio antennas with in each case three ultrasonictransmitters can be switched through three times per cycle in an aisle.Through the use of clusters 1 to 24, however, the ultrasonictransmitters of the same cluster can be switched simultaneously. A radioantenna 120 to 162 and three ultrasonic antennas or ultrasonictransmitters 1 a to 7 b are referred to as a device hereinafter.

The main aisle 102 is numbered as finger “18”. The transverse aisle 104is numbered as finger “01”. The transverse aisle 104 is numbered asfinger “02”, etc. As a result, it is possible to form identificationsfor the designation of an ultrasonic antenna, for example, theidentification: 013 a, for designating the first ultrasonic transmittera in the third device of the transverse aisle 104.

The main aisle 102 and the transverse aisles 104, 106, 110 all have awidth of, for example, 2.80 meters and the main aisle 102 has a lengthof 38 meters. The transverse aisle 104 has a length of 19.2 meters andthe transverse aisle 108 has a length of 33 meters.

The devices with the radio antennas 120 to 126 and also further devices170 (not illustrated) are arranged in the main aisle 102. The ultrasonictransmitters are designated in a row 172, beginning with 1 a, 1 b, 1 c,2 a, 2 b, and others. A row 174 serves for representing numbers thatspecify the cluster association of the ultrasonic transmitters in themain aisle 102. Thus, the ultrasonic transmitter 1 a is associated withthe cluster 15, the ultrasonic sensor 1 b is associated with the cluster16, etc. Only 24 of the at most 36 possible clusters are used, so that,in the main aisle 102, the ultrasonic transmitter 4 b is associated withthe cluster 1 and the ultrasonic transmitter 4 c is associated with thecluster 2, etc.

The transverse aisle 106 branches off from the main aisle 102 at theultrasonic transmitter 1 a of the main aisle 102. The first ultrasonictransmitter 1 a in the transverse aisle 104 is assigned to the cluster1, resulting in small influences on the ultrasonic signals of differentaisles on account of the offset during the transmission of theultrasonic pulses. Equally, the first ultrasonic sensor 1 a of thetransverse aisle 108 is assigned to a different cluster, namely thecluster 15, than the ultrasonic transmitters 2 c, 3 a, 3 b of the mainaisle 102 that are closest to said ultrasonic transmitter 1 a, theseultrasonic transmitters being assigned to the cluster 20, 21 and 22,respectively. The ultrasonic transmitters of the clusters 1 to 24 aredriven in ascending order.

The devices with the radio antennas 130 to 136 are arranged in thetransverse aisle 104. The ultrasonic transmitters are designated in arow 182, beginning with 1 a, 1 b, 1 c, 2 a, 2 b, etc. to 4 c. A row 184serves to represent numbers that specify the cluster association of theultrasonic transmitters in the main aisle 102. Thus, the ultrasonictransmitter 1 a is associated with the cluster 1 and the ultrasonicsensor 1 b is associated with the cluster 2, etc.

The devices with the radio antennas 150 to 162 are arranged in thetransverse aisle 108. The ultrasonic transmitters are designated in arow 192, beginning with 1 a, 1 b, 1 c, 2 a, 2 b, etc. to 7 b. A row 194serves to represent numbers that specify the cluster association of theultrasonic transmitters in the main aisle 102. Thus, the ultrasonictransmitter 1 a is associated with the cluster 15 and the ultrasonicsensor 1 b is associated with the cluster 16, etc. Only 24 of the atmost 36 possible clusters are used, so that, in the transverse aisle108, the ultrasonic transmitter 4 b is associated with the cluster 1 andthe ultrasonic transmitter 4 c is associated with the cluster 2, etc.

Between the transverse aisles 104 and 108, too, the arrangement workswith a cluster offset in order to avoid disturbances of the ultrasonicmeasurements. The offset amounts to ten clusters, so that nineultrasonic transmitters of an aisle always lie between the respectivelysimultaneously transmitting ultrasonic transmitters of a cluster in theevent of a parallel displacement of one aisle to the other aisle.

FIG. 2 shows a locating arrangement 198, forming the device with theradio antenna 130, in a manner representative of the arrangement of themutually identically constructed devices 120 to 162, 170, 180 and 190.The devices of an aisle are arranged one after the other along astraight line. The devices may be mounted on a ceiling or a wall.

There is a distance A3 of 1.6 meters between the ultrasonic transmitter1 a and the ultrasonic transmitter 1 b. There is equally a distance A4of 1.6 meters between the ultrasonic transmitter 1 b and the ultrasonictransmitter 1 c. The radio antenna 130 is arranged at a distance A6 of0.8 meter from the ultrasonic transmitter 1 c and thus lies precisely inthe center between the ultrasonic transmitters 1 b and 1 c. The radioantenna 132 of the adjacent device is at a distance of 4.8 meters fromthe radio antenna 130.

FIG. 3 shows constituent parts of a drive and evaluation unit 220, whichcontains the following components besides a data processing system (notillustrated) e.g. based on the operating system Windows 2000:

a so-called switch 222 of a data transmission network at which the dataprocessing system is operated as well;

a plurality of connection units connected to the switch 222, fourconnection units 230 to 236 of which are illustrated in FIG. 3. Furtherconnection units 238 connected to the switch 236 are indicated by dots;

a plurality of devices or antenna modules with a respective radioantenna 130 to 136 and in each case three ultrasonic transmitters, ineach case four devices being connected to a connection unit 230 to 238;

drive units 240 to 246 that are contained in a respective device orantenna module and in each case drive the three ultrasonic transmittersof a device, for example, the drive unit 240 of the device with theradio antenna 130 drives the ultrasonic transmitters 1 a, 1 b and 1 c;and

a power supply unit 240 for supplying power to the connection units 230to 238 and the drive units 240 to 246.

FIG. 4 shows an identification unit 300 or a DisTag having a housing302, to which is fitted a display 304 for representing five lines 308 to316 of alphanumeric text. The identification unit 300 additionally alsocontains four operating keys 320 to 326 that may function, for example,as menu selection keys.

Furthermore, the identification unit 300 contains an ultrasonic receiver330, with the aid of which the propagation time measurement is carriedout. Two light-emitting diodes 332 and 334 serve for the identificationof batch boxes sought and the identification of urgent batches,respectively. The identification unit additionally contains atransmitting/receiving antenna 302 for communication with the radioantennas 120 to 162. The identification unit 300 is fed by an internalbattery, an accumulator and, possibly, by a solar cell. Situated withinthe identification unit 300 is a circuit that provides the functions ofthe identification unit, in particular:

the propagation time measurement, including a synchronization;

the transmission of the results of the propagation time measurement; and

the reception of messages that are represented on the display 304.

In FIG. 4, the identification of the identification unit 300 isdisplayed in the top left corner of the display 304 or in the line 308.In the exemplary embodiment, the identification “123” is displayed,corresponding to a batch number.

In the display 304, line 310, the word “position” is represented in thecurrent menu selection. Line 312 contains the text “finger 02”, i.e. thespecification of the finger or transverse aisle 108 in which theidentification unit 300 is currently situated.

The fourth line 314 displays the text “x=34.50 m” because a distance of34.50 meters between the identification unit 300 and the start of thetransverse aisle 108 has been determined. The fifth line 316 serves fordisplaying control symbols 350 to 354 for operating the identificationunit 300.

FIG. 5 shows the trigonometrical basic principle for determining thelinear position. In order to achieve a maximum performance, i.e. amaximum communication rate and at the same time an accuratelocalization, with the batch tracking system, the US transmitterdensity, i.e. the number of US transmitters per unit area, must bereduced as far as possible. For this reason, a colinear arrangement ofthe US transmitters in the longitudinal direction of the fingers/aisles104, 106, 108 is effected, in the case of which only the position in thelongitudinal direction of the finger/aisle 104, 106, 108 is specifiedprecisely and unambiguously.

The intersection of two spheres 400 and 402, whose radius is calculatedfrom the US propagation time between a US transmitter 7 a and theidentification unit 300 and between a further US transmitter 7 b and theidentification unit 300, yields a ring 404 that is perpendicular to thelongitudinal axis of the finger or aisle. The distance from therespective transmitter is determined from each propagation time by meansof the formula:

propagation time*US speed=distance.

At 21 degrees Celsius, the propagation time amounts to 343.96 m/s(meters per second).

The US transmitters may be, for example, adjacent US transmitters ortransmitters separated only by one intervening ultrasonic transmitter,for example, the US transmitters 7 a and 7 b in the transverse aisle108, i.e. in the finger “102”. The spheres 400, 402 may have the sameradius r1, r2 as the identification unit is currently situated preciselyhalfway between the US transmitters 7 a and 7 b. At other positions, thespheres 400, 402 have mutually different radii. The followinggeometrical considerations hold true, however, for all sphere radii r1,r2. Therefore, with the “linear concept”, in principle two USpropagation times suffice for calculation of the precise position of anidentification unit 300.

The US transmitters are arranged at a fixed distance L of in each case1.6 meters in the center of the transverse aisle 108 parallel to theaisle direction. If two propagation time measurements of two UStransmitters with a defined distance LM are present for a DisTag 300, inwhich case LM=L*n holds true, where n is a natural number, then it ispossible to calculate the position of the DisTag 300 in the transverseaisle 108 by formulating Pythagoras theorem for the right-angledtriangles made from the sections 410, 412 (distance between DisTag 300and the transmitter 7 a determined from the propagation time of theultrasonic pulse coming from the transmitter 7 a) and 414 and also thesections 410, 416 (distance between DisTag 300 and the transmitter 7 bdetermined from the propagation time of the ultrasonic pulse coming fromthe transmitter 7 b) and 418. The section 414 designates the x distancefrom the transmitter 7 a. The section 418 designates the x distance fromthe transmitter 7 b.

The sections 414 and 418 depend on one another by way of the distance LMand the position x, in which case in FIG. 5 the following holds true forthe length of the section 414 equal to x:

length of the section 414=LM−x.

The length of the section 410 does not have to be determined. Theposition x can thus be calculated from the relationships specified. Thecalculation is independent of the y position (laterally transverse withrespect to the longitudinal axis) or the z position (height) of theidentification unit 300 in the transverse aisle 108.

Errors in determining the positions can be avoided if the location iscalculated repeatedly for an identification unit per cycle. A validvalue is defined only upon correspondence of the locations determined ofan identification unit. By way of example, the main cycle of 30 secondsis therefore subdivided once again into three subcycles each of 10seconds. By virtue of this procedure, identification units 300 currentlyin motion can be exempted from the locating until the end of themovement. Moreover, reflections and other sources of disturbance thusinfluence the results to a lesser extent.

FIG. 6 shows method steps for calculating the position of theidentification unit. In method steps 500 and 502, the propagation timeis determined by an identification unit and reported to the central dataprocessing system via the radio antennas 120 to 162. In the method step500, the propagation time of the received US signals is determined bythe DisTag, for example, the DisTag 300 having the ID (identifier) 123determines a propagation time of 12 ms in the time slot 13 and apropagation time of 14 ms in the time slot 18. The time slot 13 relatese.g. to the US transmitter 7 a and the time slot 18 relates e.g. to theUS transmitter 7 b in the transverse aisle 108. In the method step 502,the propagation times determined are transmitted to the data processingsystem in the form of a telegram via radio.

In a subsequent method step 504, the field strengths are determined bythe connection units 230 to 238. By way of example, the radio antenna162 or, with the nomenclature introduced above, the antenna RF 0207receives a reception signal from the DisTag 300 with a level of 45 dB.The antenna with the second strongest reception level may be the antenna160, i.e. the antenna RF 0206, with a reception level of 30 dB.

Afterward, in method steps 506 to 510, a coarse localization is carriedout by the data processing system, which is also referred to as a BTSserver (box tracking server). In the method step 506, a check is made toascertain whether the field strength of the strongest reception levelexceeds the field strength of the second strongest reception level by 10dB. If this is the case, then the method step 506 is followed directlyby the method step 508, in which a telegram of a DisTag is assigned toan RF antenna in the layout of the factory building. The telegram of theDisTag 300 may be assigned to the US transmitter a at the RF antenna 7or 162 in the finger or transverse aisle 108.

By contrast, if it is ascertained in the method step 506 that the levelcondition is not fulfilled, then a different localization method is usedor the next reception of a telegram from the relevant DisTag is awaited.

In the subsequent method steps 512 and 514, the fine localization iscarried out by the BTS server. In the method step 512, the BTS serverdetermines the antenna 162 on the basis of the layout data of thefactory building 100, see FIG. 1. In the subsequent method step 514, theBTS server carries out the calculations explained with reference to FIG.5. During the calculation, the simpler method with only two propagationtimes is carried out in place of a trilateration. The locating text“finger 02; x=34.5 m” is created by the BTS server.

Method steps 516 to 520 are then carried out, in which a publicationdecision is taken by the BTS server. In the method step 516, a check ismade to ascertain whether the position of the DisTag 300 has changedsince the last cycle. If the position of the DisTag 300 has changedsince the last cycle, then in the method step 518, the position isupdated in a database and the locating text is transmitted to the DisTag300. By contrast, if the position has remained the same, then the methodstep 516 is followed directly by the method step 520, in which anupdating of the database and a publication of the locating text do notoccur.

The communication of the propagation times of e.g. up to 2000 DisTags iscarried out e.g. according to the known slotted ALOHA method. By way ofexample, 100 time slots per cycle are subdivided into in each case 20sub-time slots. Each DisTag transmits in a randomly determined timeslot, so that, because of the resulting uniform distribution, despiteidentically constructed and identically operating DisTags, the DisTagscan for the most part transmit the propagation times determined. Absentmessages can be avoided by virtue of the redundancy mentioned above. Asan alternative, however, use is also made of a method in which eachDisTag is assigned a dedicated sub-time slot.

Accordingly, while several embodiments of the present invention havebeen shown and described, it is obvious that many changes andmodifications may be made thereunto without departing from the spiritand scope of the invention.

1. An identification unit comprising: a memory unit operable to store anidentification that distinguishes the identification unit from otheridentically constructed identification units; an ultrasonic receiver; aradiation transmitter; a radiation receiver; and a control unit operableto carry out an ultrasound propagation time measurement depending on asynchronization signal received by the radiation receiver and operableto transmit a result with the aid of the radiation transmitter, whereinat least one of a luminous unit and an optical signaling unit is drivenvia the radiation receiver.
 2. The identification unit according toclaim 1, further comprising a bistable character display unit operableto display a content to be represented even after an operating voltagehas been switched off.
 3. The identification unit according to claim 1,wherein the radiation transmitter comprises an electromagnetic radiationtransmitter.
 4. The identification unit according to claim 1, whereinthe radiation receiver comprises an electromagnetic radiation receiver.5. The identification unit according to claim 1, wherein the radiationtransmitter comprises an electromagnetic radiation transmitter and theradiation receiver comprises an electromagnetic radiation receiver. 6.The identification unit according to claim 1, wherein said at least oneof said luminous unit and said optical signaling unit is operable toidentify a manufacturing batch to be processed preferentially.
 7. Theidentification unit according to claim 1, wherein said at least one ofsaid luminous unit and said optical signaling unit comprises a flashingunit operable to distinguish the identification unit from said otheridentically constructed identification units at a distance of severalmeters.
 8. The identification unit according to claim 1, wherein said atleast one of said luminous unit and said optical signaling unit comprisea first light emitting diode for identifying a manufacturing batch beingsought and a second light emitting diode for identifying an urgentmanufacturing batch.